System and method for regenerative ejector based cooling cycle

Abstract

Systems and methods for a regenerative ejector-based cooling cycle that utilizes an ejector as a driving force in the cooling loop to regenerate subcooling of the refrigerant in a single-stage cooling cycle.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application, PCT Application Nos. PCT / US20 / 62972 and PCT / US21 / 49010, and U.S. Patent Nos. 10,514,201, 10,533,793, 10,465,983, and 10,514,202 (each incorporated herein by reference) are commonly assigned to Bechtel Energy Technologies and Solutions, Inc. Technical Field

[0003] The present disclosure generally relates to systems and methods for a regenerative ejector-based cooling cycle. More specifically, the systems and methods utilize an ejector as the driving force in the cooling circuit to regeneratively sub-cool the refrigerant in a single-stage cooling cycle. Background Art

[0004] The use of heat exchangers to modify the thermodynamic performance of a cooling cycle is well known. An exemplary heat exchanger in a conventional cooling cycle is called a suction line heat exchanger (SLHX). The purpose of the SLHX is to preheat the refrigerant before it enters the compressor.

[0005] Other concepts have been proposed for subcooling the refrigerant using a heat exchanger in a cooling cycle using an ejector. For example, in FIG1 , a heat exchanger is used in a system 100 for use in a conventional two-stage cooling cycle with an ejector to subcool the refrigerant and reduce the overall power consumption of the system, which is also known as cascade cooling.

[0006] The vapor first refrigerant enters the first compressor 104 from the vaporized first refrigerant line 102 and is compressed to an evaporation pressure determined by ambient conditions. The compressed vapor first refrigerant passes through the compressed first refrigerant line 106 to a heat exchanger known as an evaporative condenser 108. The condensed liquid first refrigerant passes through the condensing refrigerant line 110 to the first expansion valve 107 and / or ejector 114 based on a control valve (not shown).

[0007] The condensed liquid first refrigerant expands as it passes through expansion valve 107. The expanded two-phase first refrigerant passes through first expanded first refrigerant line 118 to a heat exchanger called cascade exchanger 132, where it is vaporized by the heat and used to cool the second refrigerant from compressed second refrigerant line 130, which forms part of the second stage of the cooling cycle. The vaporized first refrigerant passes through vaporized first refrigerant line 102 to compressor 104.

[0008] The condensed liquid first refrigerant enters the ejector 114 as a motive fluid where it mixes with vaporized first refrigerant from another vaporized first refrigerant line 126 and is ejected from the ejector 114 as a two-phase first refrigerant. The two-phase first refrigerant passes through a two-phase first refrigerant line 116 to a flash economizer 112 where it is flashed into vapor first refrigerant and liquid first refrigerant. The vapor first refrigerant from the flash economizer 112 passes through the vaporized first refrigerant line 102 to the compressor 104. The liquid first refrigerant from the flash economizer 112 passes through a liquid first refrigerant line 120 to a second expansion valve 121. The liquid first refrigerant expands as it passes through the second expansion valve 121. The expanded two-phase first refrigerant passes through a second expanded first refrigerant line 122 to a heat exchanger called a subcooler 124 where it is vaporized by heat and used to cool second refrigerant from a cooled second refrigerant line 134 that forms part of a second stage of a cooling cycle. The vaporized first refrigerant from the subcooler 124 passes through another vaporized first refrigerant line 126 to the ejector 114.

[0009] The vaporized second refrigerant passes through a vaporized second refrigerant line 128 to a second compressor 136. The compressed vapor second refrigerant passes through a compressed second refrigerant line 130 to a cascade heat exchanger 132 where it is cooled. The cooled liquid second refrigerant passes through a cooled second refrigerant line 134 to the subcooler 124 where it is further cooled. The subcooled liquid second refrigerant from the subcooler 124 passes through a subcooled second refrigerant line 135 to a third expansion valve 138. The expanded two-phase second refrigerant passes through an expanded second refrigerant line 139 to a heat exchanger called an evaporator 140 where it is vaporized by heat into vaporized second refrigerant. Thus, the two-stage cooling cycle system 100 requires two cascade cooling circuits and one refrigerant for each respective stage. BRIEF DESCRIPTION OF DRAWINGS

[0010] A detailed description will now be described with reference to the accompanying drawings, in which like elements are referred to by like reference numbers, in which:

[0011] FIG. 1 is a schematic diagram illustrating a system for use in a conventional two-stage ejector-based cooling cycle.

[0012] Figure 2 is a schematic diagram illustrating one embodiment of a system for use in a single-stage regenerative ejector-based cooling cycle.

[0013] Figure 3 is a comparison Figure 2The illustrated system and conventional four (4) component cooling cycle at the expected pressure / enthalpy of the state points.

[0014] Figure 4 is Figure 2 the schematic diagram of the system in Figure 3 is replaced with the corresponding state points in

[0015] Figure 5 is a schematic diagram illustrating one embodiment of a system for use in two combined single-stage regenerative ejector-based cooling cycles. DETAILED DESCRIPTION

[0016] The subject matter of the present disclosure is particularly described, however, the description is not intended to limit the scope of the present disclosure. Thus, the subject matter described herein can also be embodied in other ways, including different structural, step and / or combination of steps, and in connection with other existing or future technologies. Although the term "step" can be used herein to connote different elements of methods employed, the term should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except the specification specifies otherwise. Other features and advantages of the disclosed embodiments will be apparent from the following drawings and detailed description, and from the claims. All these additional features and advantages will be included within the scope of the disclosed embodiments. Moreover, the illustrated figures are merely examples and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different embodiments can be implemented. As to the temperatures and pressures referenced in the following description, these conditions are merely illustrative and are not meant to limit the present disclosure.

[0017] Thus, the systems and methods disclosed herein improve upon the conventional two-stage cooling cycle by utilizing an ejector as the driving force for the refrigerant in a single-stage cooling cycle to regenerate subcooling. The systems and methods disclosed herein achieve the same or higher energy efficiency as the conventional two-stage cooling cycle, but with fewer components because the second stage is not needed to achieve the subcooling effect. The single-stage cooling cycle disclosed herein also does not require a high entrainment ratio ejector, which reduces the compression ratio and improves the energy efficiency of the cooling cycle.

[0018] In one embodiment, the present disclosure includes a system for use in a single stage cooling cycle comprising: i) a single refrigerant; ii) an ejector for mixing the single refrigerant in a condensed liquid form with the single refrigerant in a first vaporized form to form the single refrigerant in a two-phase form; iii) a flash economizer in fluid communication with the ejector for separating the single refrigerant in the two-phase form from the ejector into the single refrigerant in a second vaporized form and the single refrigerant in a liquid form; iv) an expansion valve in fluid communication with the flash economizer for converting a portion of the single refrigerant in the liquid form into the single refrigerant in an expanded two-phase form; and v) a subcooler in fluid communication with the expansion valve for cooling another portion of the single refrigerant in the liquid form by transferring heat from the other portion of the single refrigerant in the liquid form to the single refrigerant in the expanded two-phase form and producing the single refrigerant in the first vaporized form and the single refrigerant in a separate subcooled liquid form.

[0019] In another embodiment, the present disclosure includes a single stage cooling method comprising: i) mixing a single refrigerant in a condensed liquid form with the single refrigerant in a first vaporized form to form the single refrigerant in a two-phase form; ii) separating the single refrigerant in the two-phase form into the single refrigerant in a second vaporized form and the single refrigerant in a liquid form; iii) converting a portion of the single refrigerant in the liquid form into the single refrigerant in an expanded two-phase form; and iv) cooling another portion of the single refrigerant in the liquid form by transferring heat from the other portion of the single refrigerant in the liquid form to the single refrigerant in the expanded two-phase form and producing the single refrigerant in the first vaporized form and the single refrigerant in a separate subcooled liquid form.

[0020] Reference is now made to Figure 2 , which shows one embodiment of a system 200 for use in a single stage regenerative ejector-based cooling cycle with a single refrigerant. One exemplary refrigerant is R-134A refrigerant with a cooling load of 5.4 MW for cooling a circulating water cooling system from 30°C (86°F) to 22°C, but other refrigerants can also be used.

[0021] Vapor refrigerant enters compressor 204 from first vaporized refrigerant line 202 and is compressed to a pressure of 114 psig and a temperature of 107°F. Compressed vapor refrigerant passes through compressed refrigerant line 206 to a heat exchanger called evaporative condenser 208. Condensed liquid refrigerant passes through condensed refrigerant line 210 to ejector 214 at a temperature of 95°F with the help of pump 207. Due to the flexibility provided by pump 207 and ejector 214, system 200 can achieve higher coefficient of performance and lower energy consumption than conventional systems. Thus, pump 207 enables a higher discharge pressure of ejector 214 and a higher intermediate pressure of flash economizer 212. Optionally, pump 207 can be removed based on capital cost, maintenance issues, and / or system limitations.

[0022] Condensed liquid refrigerant enters ejector 214 as motive fluid where it mixes with vaporized refrigerant from second vaporized refrigerant line 226 and is ejected from ejector 214 as two-phase refrigerant. The motive fluid will always be liquid as it is directly downstream of evaporative condenser 208. The two-phase refrigerant passes through two-phase refrigerant line 216 to flash economizer 212 where it is flashed into vapor refrigerant and liquid refrigerant. Optionally, a throttling valve can be used for operational flexibility.

[0023] Vapor refrigerant from flash economizer 212 enters compressor 204 through first vaporized refrigerant line 202. Liquid refrigerant from flash economizer 212 passes through liquid refrigerant line 220 to pump 222. Optionally, flash economizer 212 and pump 202 can be unnecessary for smaller cooling cycles and thus removed. Liquid refrigerant is pumped to expansion valve 223 and / or subcooler 224 based on control valves (not shown).

[0024] Liquid refrigerant expands as it passes through expansion valve 223. The expanded two-phase refrigerant passes through expanded refrigerant line 225 to subcooler 224 where it is vaporized by heat and used to cool liquid refrigerant from pump 222. Vaporized refrigerant from subcooler 224 passes through second vaporized refrigerant line 226 to ejector 214.

[0025] Subcooled liquid refrigerant from subcooler 224 passes through subcooled refrigerant line 228 to evaporator 230 where it is vaporized by heat into vaporized refrigerant that passes through third vaporized refrigerant line 232 to flash economizer 212 where it is ultimately recirculated back to compressor 204 through first vaporized refrigerant line 202. System 200 requires a single refrigerant and thus, there are fewer components than conventional system 100 used in two-stage ejector-based cooling cycles that are less economical and efficient in cooling.

[0026] Figure 3 The pressure-enthalpy diagram in FIG. 4 compares the expected pressure / enthalpy values at the state points of the system 200 shown in FIG. 2 and a conventional four (4) component cooling cycle. Figure 2 The dashed lines connect the state points of the system 200, and the dashed / dotted lines connect the state points of the conventional 4 component cooling cycle. The bubble point line represents the line beyond which the post refrigerant is liquid. The dew point line represents the line beyond which the refrigerant is vapor.

[0027] In FIG. 4, Figure 4 the system 200 is shown with reference numerals replaced by corresponding state points in FIG. 4. Notably, the transition of the refrigerant from state point 040 to state point 010 by means of the subcooler 224 facilitates a higher inlet pressure at the compressor 204 at state point 001, and a subsequent reduction in the differential pressure between state points 001 and 002. In comparison to state point 008 in the conventional 4 component cycle shown in FIG. 4, Figure 2 state point 0010 of the system 200 indicates that a single refrigerant in the system 200 achieves the same cooling temperature as the conventional 4 component cycle, while operating at a higher pressure than the conventional 4 component cycle, thereby reducing compression energy. Figure 3 Figure 3 Table 1 below compares the expected performance of a conventional 4 component cooling cycle and a single stage regenerative ejector based cooling cycle shown in FIG. 2 using a simulation model (Aspen HYSYS version 12.1) with predicted ejector performance. As the expected results indicate,

[0028] the single stage regenerative ejector based cooling cycle shown in FIG. 2 will achieve higher performance coefficients with lower generation of compression power. Figure 2 Figure 2

[0029]

[0030] By replacing the evaporator 230 in one cooling cycle and the evaporative condenser 208 in another cooling cycle with a single cascading exchanger 502 as shown in FIG. 5, Figure 5 the system 200 in FIG. 2 can be combined with another single stage regenerative ejector based cooling cycle, like the single stage regenerative ejector based cooling cycle shown in FIG. 2, which enables cooling at lower temperatures, such as for example in ultra-low temperature applications using independent refrigerants. Figure 2 Figure 2

[0031] ​​​​​While the present disclosure has been described in connection with the presently preferred embodiments, those skilled in the art will understand that the present disclosure is not intended to limit the disclosed embodiments. Retrofitting or modification of existing ejector-based cooling cycles can be made in accordance with the disclosure herein, which can also be implemented in any other refrigeration process for heating or cooling in a closed structure to achieve similar results. Accordingly, it is contemplated that various alternative embodiments and modifications to the disclosed embodiments can be made without departing from the spirit and scope of the present disclosure as defined in the appended claims and their equivalents.

Claims

1. A system for use in a single stage cooling cycle, comprising: a single refrigerant; an ejector for mixing a single refrigerant in a condensed liquid form and a single refrigerant in a first vaporized form to form a single refrigerant in a two-phase form; a flash-type economizer in fluid communication with the ejector for separating the single refrigerant in the two-phase form from the ejector into a single refrigerant in a second vaporized form and a single refrigerant in a liquid form; an expansion valve positioned between a liquid refrigerant line connected to the flash-type economizer and a subcooler for converting a portion of the single refrigerant in the liquid form from the liquid refrigerant line into a single refrigerant in an expanded two-phase form; and an evaporator in fluid communication with the subcooler for heating a separate single refrigerant in a subcooled liquid form by transferring heat from an external source to the separate single refrigerant in a subcooled liquid form and producing a single refrigerant in a third vaporized form, wherein the flash-type economizer is connected to the evaporator for receiving the single refrigerant in the third vaporized form.

2. The system of claim 1, further comprising a pump positioned between the flash-type economizer and the subcooler for distributing the single refrigerant in the liquid form.

3. The system of claim 1, further comprising a compressor connected to the flash-type economizer for compressing the single refrigerant in the second vaporized form.

4. The system of claim 1, further comprising a pump positioned upstream of the ejector for increasing at least one of a discharge pressure at the ejector and an intermediate pressure at the flash-type economizer.

5. The system of claim 1, wherein, the temperature and pressure of the single refrigerant in the second vaporized form are approximately 72°F and approximately 89 psia, respectively.

6. The system of claim 1, wherein, the temperature and pressure of the single refrigerant in the liquid form are approximately 95°F and approximately 129 psia, respectively.

7. The system of claim 1, wherein, the temperature and pressure of the single refrigerant in the subcooled liquid form are approximately 68°F and approximately 88 psia, respectively.

8. The system of claim 1, wherein, the temperature and pressure of the single refrigerant in the two-phase form are approximately 72°F and approximately 89 psia, respectively.

9. A single stage cooling method, comprising: mixing a single refrigerant in a condensed liquid form and a single refrigerant in a first vaporized form to form a single refrigerant in a two-phase form; separating the single refrigerant in the two-phase form and a single refrigerant in a second vaporized form into a single refrigerant in a third vaporized form and a single refrigerant in a liquid form; converting a portion of the single refrigerant in the liquid form into a single refrigerant in an expanded two-phase form; cooling another portion of the single refrigerant in the liquid form by transferring heat from the other portion of the single refrigerant in the liquid form to the single refrigerant in the expanded two-phase form and producing the single refrigerant in the first vaporized form and a separate single refrigerant in a subcooled liquid form; and heating the separate subcooled liquid form of single refrigerant by transferring heat from an external source to the subcooled liquid form of single refrigerant and producing the third vaporized form of single refrigerant.

10. The method of claim 9, further comprising compressing the second vaporized form of single refrigerant.

11. The method of claim 9, further comprising at least one of increasing discharge pressure at the ejector and intermediate pressure at the flash economizer with a pump.

12. The method of claim 9, wherein, The temperature and pressure of the second vaporized form of single refrigerant are approximately 72 °F and approximately 89 psia, respectively.

13. The method of claim 9, wherein, The temperature and pressure of the liquid form of single refrigerant are approximately 95 °F and approximately 129 psia, respectively.

14. The method of claim 9, wherein, The temperature and pressure of the separate subcooled liquid form of single refrigerant are approximately 68 °F and approximately 88 psia, respectively.

15. The method of claim 9, wherein, The temperature and pressure of the two-phase form of single refrigerant are approximately 72 °F and approximately 89 psia, respectively.

16. The method of claim 9, wherein, The temperature and pressure of the first vaporized form of single refrigerant are approximately 60 °F and approximately 72 psia, respectively.

17. The method of claim 9, wherein, The single refrigerant is a refrigerant with a cooling load of 5.4 MW for cooling a circulating water system from approximately 86 °F to approximately 72 °F.

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